The present invention relates to automatic fastening devices, and in particular a fastening device that drives a fastener into a workpiece by effecting multiple blows upon the fastener.
The most typical type of nailing or fastening device is that of the xe2x80x9csingle strokexe2x80x9d type. In these types of devices, a striker assembly is driven to fasten a fastener into a workpiece with a single blow or impact. The disadvantage of these devices is that they require very high levels of impact energy, especially when longer fastener lengths are to be used.
There have been some attempts to provide a xe2x80x9cmulti-strokexe2x80x9d fastening device, which employs a striker assembly, which is driven to provide a plurality of blows or impacts upon the fastener head for progressively fastening the fastener into a workpiece. Such devices have been proposed by U.S. Pat. Nos. 4,183,453; 4,724,992; 2,796,608; 3,203,610; 1,767,485; and 4,807,793. The disadvantage with these proposed devices is that the fastener striker assembly is driven through a plurality of driving strokes, the lengths of the strokes are progressively increased as the fastener is progressively driven into the workpiece. As a result, the timing for driving the striker assembly becomes more difficult to manage. In addition, because the stroke length of the striker assembly increases during the course of each fastening cycle, the xe2x80x9cfeelxe2x80x9d of the tool is somewhat irregular. It is an object of the invention to overcome the difficulties noted above.
In accordance with this object, the present invention provides a multi-stroke fastening device for driving fasteners into a workpiece. This multi-stroke fastening device provides a housing, a fastener drive track carried by the housing, a striker assembly guide track mounted within the housing, a striker assembly mounted in slidable relation within said guide track, a power drive assembly, and a feed mechanism. The striker assembly includes a driver member constructed and arranged to strike a fastener disposed in the fastener drive track. The striker assembly is constructed and arranged to be moved along the guide track through a plurality of alternating drive strokes and return strokes to effect a plurality of impacts of the driver member upon the fastener in order to drive the fastener into the workpiece. The striker assembly has a substantially constant drive stroke lengths relative to the guide track. The power drive assembly is constructed and arranged to drive the striker assembly to effect the plurality of impacts of the driver member upon the fastener, and the feed mechanism is constructed and arranged to feed successive fasteners into the drive track to be struck by the striker assembly.
It is also an object of the invention to provide a multi-stroke fastening device which includes a striker assembly having a drive stroke length which does not progressively increase as the fastener is progressively driven into the workpiece.
It is a further object of the invention to provide a multi-stroke fastening device in which the power drive assembly is resiliently coupled to the striker assembly to maintain a predetermined range of distance therebetween.
Prior art fastening devices that drive a fastener into a workpiece with a single blow need not be concerned with the fastener driver maintaining a coupled relation with respect to the fastener being driven. Multi-blow fastening devices, on the other hand are presented with a unique problem in that if a plurality of fastening impacts are to be imparted upon a single fastener in order to drive the fastener into the workpiece, the tool tends to bounce off the fastener head with each drive stroke. This may lead to an inefficient and rather clumsy operation of the tool.
It is a further object of the present invention to provide multi-blow fastening tool that overcomes the problem noted above. In accordance with this object, the present invention provides a multi-stroke fastening device for driving fasteners into a workpiece, comprising a housing, a striker assembly guide track mounted within the housing, and a striker assembly mounted in slidable relation with respect to the guide track. The striker assembly includes a driver member constructed and arranged to strike a fastener to be driven into a workpiece. The striker assembly is moveable along the guide track through a plurality of alternating drive strokes and return strokes to effect a plurality of impacts of the driver member upon the fastener. A power drive assembly is constructed and arranged to drive the striker assembly through the plurality of alternating drive strokes and return strokes to effect the plurality of impacts of the driver member upon the fastener. A nose assembly is carried by the housing and defines a fastener drive track along which the driver travels during the drive strokes and return strokes. Furthermore, a faster head engaging structure is constructed and arranged to engage a portion of the head of the fastener to be driven at least during the return stroke. A resilient structure is operatively coupled to the fastener head engaging structure. The resilient structure is constructed and arranged to permit limited longitudinal movement of the fastener head engaging structure relative to the striker assembly guide track, and dampens impact of engagement between the fastener head engaging structure and the head of the fastener to be driven.
It is a further object of the present invention to provide a multi-stroke fastening device that employs a fastener impacting driver assembly that is pneumatically coupled to the driving structure so that impacts of the driver assembly are very effectively damped to reduce vibrations and shock in the system. In accordance with this object, the present invention provides a multistroke fastening device for driving fasteners into a workpiece, comprising a housing. The nose assembly is carried by the housing and defines a drive track. A fastener feed mechanism includes a fastener feed pawl that moves successive fasteners into the drive track. A cylinder guide track is mounted within the housing, the cylinder guide track having a forward end and a rearward end. A driver assembly is disposed in slidably sealed relation with the cylinder guide track, the driver assembly being movable forwardly through the cylinder drive track during a fastener impacting drive stroke thereof and movable rearwardly through the cylinder guide track during a return stroke thereof. The driver assembly includes a driver member movable through the drive track during alternating drive strokes and return strokes to impart a plurality of impacts upon a fastener to be driven into the workpiece so as to drive the fastener into the workpiece. A piston is disposed in slidably sealed relation with the cylinder guide track, the piston being rearwardly spaced from the driver assembly, with an air space disposed between the piston and driver assembly. A motor is operatively connected with the piston and constructed and arranged to drive the piston forwardly and rearwardly through the cylinder guide track to effect the alternating drive strokes and return strokes. Movement of the piston forwardly through the cylinder guide track compresses air within the air space so as to force the driver assembly forwardly through the cylinder guide track to effect the fastener impacting drive stroke so that the driver member impacts the fastener to be driven.